All it took was one snapped rod . . .

There is nothing like closing the Bay Bridge to remind us of an inconvenient truth. San Francisco — although it may consider itself the epicenter of the Bay Area — is largely a commuter town.

Noah Berger/Special to the Chronicle

All it takes is a broken rod and Bay Bridge traffic is snarled.

Although the Census Bureau estimates the city’s population at over 808,000, it increases by nearly two thirds every working day when over 520,000 commuters make their way into the city.

Their cars jam the toll plaza at the Bay Bridge, crowd 101 and 280 on the way up from the Peninsula, and if you don’t get to a BART parking lot by eight in the morning (at least in the East Bay) you are out of luck. And that’s on a normal day.

And then, one rod snaps on the Bay Bridge and the commute is chaos. The San Mateo and Richmond-San Rafael bridges turn into parking lots. I was in an East Bay Bart parking structure this morning and drivers careening around the ramps had the panicked, wide-eyed look of deer fleeing a forest fire.

So wouldn’t this be a good time to consider a few options? You know when they trot out that old joke — take BART. Please?

Frankly, we’d love to. But there’s no place to park and there aren’t good options to ride to the stations. More parking, somewhere, would surely increase ridership.

When something like this happens it makes it clear — once again — that people in the Bay Area would be delighted to take some form of public transit. They just need a way to make it work for them.

Oh, and for those of you sitting in San Francisco as this bridge repair snarls traffic, don’t get too smug. Two-thirds of the city’s residents are renters. If statistics hold, when you get older and want to start a family, you’ll move out of the city too. And then you can wonder why this traffic mess hasn’t been addressed.